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package com.sun.mail.util;

import com.song.util.CheckMessyCode;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.nio.charset.StandardCharsets;

/**
 * 重写LineInputStream，当邮件中存在中文明文编码时候出现乱码。在原类基础上增加判断字符串是否乱码，如果乱码编码方式改为"GBK"。 This
 * class is to support reading CRLF terminated lines that contain only US-ASCII
 * characters from an input stream. Provides functionality that is similar to
 * the deprecated <code>DataInputStream.readLine()</code>. Expected use is to
 * read lines as String objects from a RFC822 stream.
 *
 * It is implemented as a FilterInputStream, so one can just wrap this class
 * around any input stream and read bytes from this filter.
 *
 * @author John Mani
 * @author Bill Shannon
 */
public class LineInputStream extends FilterInputStream {

    private boolean allowutf8;
    private byte[] lineBuffer = null; // reusable byte buffer
    private static int MAX_INCR = 1024 * 1024; // 1MB

    public LineInputStream(InputStream in) {
        this(in, false);
    }

    /**
     * @param in
     *            the InputStream
     * @param allowutf8
     *            allow UTF-8 characters?
     * @since JavaMail 1.6
     */
    public LineInputStream(InputStream in, boolean allowutf8) {
        super(in);
        this.allowutf8 = allowutf8;
    }

    /**
     * Read a line containing only ASCII characters from the input stream. A line is
     * terminated by a CR or NL or CR-NL sequence. A common error is a CR-CR-NL
     * sequence, which will also terminate a line. The line terminator is not
     * returned as part of the returned String. Returns null if no data is
     * available.
     * <p>
     *
     * This class is similar to the deprecated
     * <code>DataInputStream.readLine()</code>
     *
     * @return the line
     * @exception IOException
     *                for I/O errors
     */
    @SuppressWarnings("deprecation") // for old String constructor
    public String readLine() throws IOException {
        // InputStream in = this.in;
        byte[] buf = lineBuffer;

        if (buf == null)
            buf = lineBuffer = new byte[128];

        int c1;
        int room = buf.length;
        int offset = 0;

        String source = null;

        while ((c1 = in.read()) != -1) {
            if (c1 == '\n') // Got NL, outa here.
                break;
            else if (c1 == '\r') {
                // Got CR, is the next char NL ?
                boolean twoCRs = false;
                if (in.markSupported())
                    in.mark(2);
                int c2 = in.read();
                if (c2 == '\r') { // discard extraneous CR
                    twoCRs = true;
                    c2 = in.read();
                }
                if (c2 != '\n') {
                    /*
                     * If the stream supports it (which we hope will always be the case), reset to
                     * after the first CR. Otherwise, we wrap a PushbackInputStream around the
                     * stream so we can unread the characters we don't need. The only problem with
                     * that is that the caller might stop reading from this LineInputStream, throw
                     * it away, and then start reading from the underlying stream. If that happens,
                     * the pushed back characters will be lost forever.
                     */
                    if (in.markSupported())
                        in.reset();
                    else {
                        if (!(in instanceof PushbackInputStream))
                            in /* = this.in */ = new PushbackInputStream(in, 2);
                        if (c2 != -1)
                            ((PushbackInputStream) in).unread(c2);
                        if (twoCRs)
                            ((PushbackInputStream) in).unread('\r');
                    }
                }
                break; // outa here.
            }

            // Not CR, NL or CR-NL ...
            // .. Insert the byte into our byte buffer
            if (--room < 0) { // No room, need to grow.
                if (buf.length < MAX_INCR)
                    buf = new byte[buf.length * 2];
                else
                    buf = new byte[buf.length + MAX_INCR];
                room = buf.length - offset - 1;
                System.arraycopy(lineBuffer, 0, buf, 0, offset);
                lineBuffer = buf;
            }
            buf[offset++] = (byte) c1;
        }

        if ((c1 == -1) && (offset == 0))
            return null;

//		if (allowutf8)
//			source = new String(buf, 0, offset, StandardCharsets.UTF_8);
//		else
//			source = new String(buf, 0, 0, offset);

        source = new String(buf, 0, offset, StandardCharsets.UTF_8);

        if (CheckMessyCode.checkMessyCode(source)) {
            source = new String(buf, 0, offset, "GB18030");
        }


        return source;

    }

}
